1. Field of the Invention
The present invention is related to monitoring the filling and discharging of material from a bunker and, more particularly, to monitoring the supply of coal from a plurality of bunkers to the burners of a boiler.
2. Description of the Related Art
There is a substantial body of knowledge on how characteristics, such as particle size, moisture content, bunker geometry, etc., affect the distribution of particulate solid material during filling and redistribution resulting from discharge of material in a bunker. However, there have been only preliminary attempts to apply this knowledge to continuously predicting the arrangement of material in a bunker. Since the material in a bunker can vary in composition and flow characteristics due to variation in the source of the material loaded into the bunker, increased knowledge of the arrangement of the material within a bunker would be useful in situations where the composition of the material discharged from the bunker are important.
For example, particulate solid materials, i.e., rocks, stored in bunkers may be mixed or blended in the production of cement. As another example, coal supplied to coal-fired boilers is typically stored temporarily in bunkers prior to feeding the burners of the boiler If the coal varies in sulphur content, knowledge of the content of the sulphur being supplied to the burners at any given time enables the operator of the boiler to avoid exceeding SO.sub.2 emission limits. Also, variations in heating value of the coal can affect how the boiler should be operated to maintain desired steam flow, temperature and pressure in the boiler.
No technique is presently available to obtain information regarding the arrangement of material in a bunker. Bulk material analyzers, available from, e.g., GAMMA-METRICS in San Diego, California, have been used in blending and sorting coal by sulphur content and in rock blending by the cement industry. However, there has been only rudimentary attempts to predict the arrangement of material in a bunker so that the material being discharged at any given time can be accurately predicted.